HEADER - Uploading a background image
At the top of all your pages (except the home page), you can upload a single image that will be used as a background of your header.
To upload it, in the Theme Settings, click on the "Settings" tab. Then choose the section called "Header" (make sure to NOT choose the "Header" that is in the "Sections" tab, it's a different one!).
You will be able to upload your own image there.